Ternary single-crystal positive electrode material, and preparation method therefor and use thereof

Abstract

The present application relates to the technical field of ternary positive electrode materials, and provides a ternary single-crystal positive electrode material, and a preparation method therefor and the use thereof. The ternary single-crystal positive electrode material has a D50 of greater than or equal to 3 μm, and dO-Li-O of equal to 2.0-3.5 A, wherein the dO-Li-O is the distance between Li atoms and O atoms of two adjacent layers; and the ternary single-crystal positive electrode material has a compression strength of greater than or equal to 150 MPa. The present application provides a ternary single-crystal positive electrode material having a good rate capability and cycle performance.

Description

A ternary single-crystal cathode material, its preparation method and application

[0001] This application claims priority to Chinese Patent Application No. 202411629821.1, filed on November 14, 2024, entitled “A Ternary Single Crystal Cathode Material and Its Preparation Method and Application”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to a ternary single-crystal cathode material, its preparation method and application, belonging to the field of ternary cathode material technology. Background Technology

[0003] In the field of ternary cathode material technology, the preparation of large single crystals is an important research topic. Due to limitations in the preparation process and other factors, existing ternary single crystal cathode materials generally suffer from low voltage resistance and poor cycle life.

[0004] Specifically, the molten salt method is a commonly used method for preparing large single crystals, belonging to the field of salt solution preparation technology. The molten salt method mainly involves heating a salt to above its melting point, making it liquid, then adding other substances and controlling parameters such as temperature and pressure to precipitate the desired crystals. However, this method is complex, has high production costs, requires the addition of eutectic agents such as LiCl, results in high residual lithium levels, and typically requires water washing after calcination. This not only wastes water resources and pollutes the environment but also damages the morphology of the single crystal, affecting its structural strength and performance. The resulting capacity and cycle performance are poor, limiting the application of single crystals in high-tech fields.

[0005] To address the aforementioned issues, several solutions have been proposed in the prior art. For example, one approach is to reduce the amount of water used during the washing process by changing the composition of the molten salt, but this approach may affect the growth rate and quality of the crystals. Another approach is to improve the growth rate and quality of the crystals by changing the cooling method, such as using rapid cooling, but this approach may increase the complexity and cost of the equipment. Summary of the Invention

[0006] This application provides a ternary single-crystal cathode material, its preparation method, and its application. As a large single-crystal cathode material with a relatively large particle size, the distance between the Li atoms and the O atoms of the two adjacent layers of this ternary single-crystal cathode material is small, resulting in high withstand voltage and good structural stability, which in turn helps to improve the cycle performance of this ternary single-crystal cathode material.

[0007] This application provides a ternary single-crystal cathode material, wherein the ternary single-crystal cathode material has a D 50 Greater than or equal to 3 μm; the d of the ternary single-crystal cathode materialO-Li-O =2.0A~3.5A, wherein, the d O-Li-O It is the distance between Li atoms and O atoms in the two adjacent layers; the withstand voltage of the ternary single crystal cathode material is greater than or equal to 150 MPa.

[0008] Optionally, the ternary single-crystal cathode material includes lithium, oxygen, and transition metal elements; the transition metal elements include nickel, cobalt, and manganese; and the chemical formula of the ternary single-crystal cathode material is Li. y Ni a Co b Mn c O2, wherein 0.98≤y≤1.10, 0.6≤a≤0.9, 0≤b≤0.4, 0≤c≤0.4; and / or, the concentration of lithium hydroxide and the concentration of lithium carbonate in the ternary single-crystal cathode material are less than or equal to 800ppm; and / or, the particle size distribution width of the ternary single-crystal cathode material is 1.10~1.30.

[0009] Optionally, the ternary single-crystal cathode material is charged at a constant current rate of 0.9–1.1C to 4.45–4.55V at 20–30°C, then charged at a constant voltage rate of 0.045–0.055C to 4.45–4.55V, and then discharged at a discharge rate of 0.9–1.1C to 2.9–3.1V. After repeating this charge-discharge cycle 500 times, the capacity retention rate is not less than 86%.

[0010] Optionally, the method includes: adding a complexing agent and a surfactant to a nickel-cobalt-manganese solution containing nickel, cobalt, and manganese compounds to obtain a mixed solution; spray-drying the mixed solution to obtain a spray material; thermally decomposing the spray material in an oxygen-containing atmosphere to obtain an oxide precursor; and sintering the oxide precursor with a lithium source to obtain the ternary single-crystal cathode material.

[0011] Optionally, the complexing agent includes one or more of citric acid, tartaric acid, and sodium tripolyphosphate; and / or, the surfactant includes one or more of polyethylene glycol, potassium thiolate, and polyethylene glycol sulfate.

[0012] Optionally, during the spray drying process, the exhaust air temperature is 150–220°C, and the atomizer frequency is 200–400 Hz; and / or, the specific surface area of ​​the spray material is 15–30 m². 2 / g; and / or, the particle size distribution width of the spray material is less than or equal to 1.5.

[0013] Optionally, the thermal decomposition temperature is 500–800°C, and the thermal decomposition time is 4–6 hours; and / or, the D of the spray material...50 and the D of the oxide precursor 50 The difference between the D of the spray material and the D of the spray material 50 The ratio is less than or equal to 20%.

[0014] Optionally, the intensity of the nickel oxide peak in the X-ray diffraction (XRD) pattern of the oxide precursor is 2500–3500 Counts.

[0015] This application provides a positive electrode sheet, which includes the ternary single crystal positive electrode material as described above or the ternary single crystal positive electrode material prepared according to the preparation method described above.

[0016] This application provides a lithium-ion battery, which includes a positive electrode as described above.

[0017] This application provides a ternary single-crystal cathode material, its preparation method, and its application, as a large-particle-size (D) cathode material. 50 A ternary single-crystal material with a diameter greater than or equal to 3 μm, wherein the distance between the Li atoms and the O atoms in the two adjacent layers of the ternary single-crystal cathode material (i.e., d) O-Li-O The smaller size helps to improve the strength of the ternary single-crystal cathode material, ensuring that its withstand voltage is greater than or equal to 150MPa, which helps to improve the structural stability of the ternary single-crystal cathode material, and thus helps to improve the cycle performance of the ternary single-crystal cathode material. Attached Figure Description

[0018] Figure 1 is an electron microscope image of the ternary single-crystal cathode material of Example 1;

[0019] Figure 2 is an electron microscope image of the ternary single-crystal cathode material of Comparative Example 1;

[0020] Figure 3 is an electron microscope image of the ternary single-crystal cathode material of Example 7. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] This application provides a ternary single-crystal cathode material, wherein the D of the ternary single-crystal cathode material is... 50 Greater than or equal to 3 μm; the d of this ternary single-crystal cathode material O-Li-O =2.0A~3.5A, where d O-Li-OIt is the distance between a Li atom and an O atom in the two adjacent layers; the withstand voltage of this ternary single-crystal cathode material is greater than or equal to 150 MPa.

[0023] According to the inventor's research and analysis: as a large particle size (D 50 A ternary single-crystal material with a diameter greater than or equal to 3 μm, wherein the distance between the Li atoms and the O atoms in the two adjacent layers of the ternary single-crystal cathode material (i.e., d) O-Li-O The smaller size helps to improve the strength of the ternary single-crystal cathode material, ensuring that its withstand voltage is greater than or equal to 150MPa, which helps to improve the structural stability of the ternary single-crystal cathode material, and thus helps to improve the cycle performance of the ternary single-crystal cathode material.

[0024] In some embodiments, the ternary single-crystal cathode material includes lithium, oxygen, and transition metal elements.

[0025] The aforementioned transition metal elements may include nickel, cobalt, and manganese.

[0026] Furthermore, the chemical formula of the aforementioned ternary single-crystal cathode material can be Li y Ni a Co b Mn c O2, where 0.98≤y≤1.10, 0.6≤a≤0.9, 0≤b≤0.4, and 0≤c≤0.4. For example, y can be a range of 0.98, 0.99, 1.00, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.10, or any two of these ranges; a can be a range of 0.6, 0.7, 0.8, 0.9, or any two of these ranges; b can be a range of 0, 0.1, 0.2, 0.3, 0.4, or any two of these ranges; and c can be a range of 0, 0.1, 0.2, 0.3, 0.4, or any two of these ranges.

[0027] In some embodiments, the residual lithium content of the ternary single-crystal cathode material is relatively low, specifically, the concentration of lithium hydroxide and the concentration of lithium carbonate in the ternary single-crystal cathode material are less than or equal to 800 ppm.

[0028] In some embodiments, the particle size distribution width (SPAN) of the ternary single-crystal cathode material is 1.10 to 1.30, which indicates a narrow particle size distribution and relatively uniform particle size.

[0029] In some embodiments, the above-mentioned ternary single-crystal cathode material is mixed with conductive carbon black and PVDF in a weight ratio of 96%:2%:2%, and a cathode slurry is obtained by dispersion. The cathode slurry is then coated on at least one functional surface of an aluminum foil current collector, with a cathode areal density of 4.12 g / cm³.3 The positive electrode sheet is prepared by rolling. Artificial graphite, styrene-diene rubber (SBR), sodium carboxymethyl cellulose, and conductive carbon black are mixed in a weight ratio of 94%:3%:2%:1%. The mixture is dispersed in water and mixed using a double planetary mixing process to obtain a negative electrode slurry. This negative electrode slurry is coated onto at least one functional surface of a copper current collector, followed by rolling and drying to obtain a negative electrode sheet. The positive electrode sheet, negative electrode sheet, and separator are assembled into a lithium-ion battery, and a non-aqueous electrolyte is injected. The electrolyte preparation process is as follows: ethylene carbonate (EC), diethyl carbonate (DEC), and propylene carbonate (PC) are mixed in a mass ratio of 2:5:3. Then, 5% of the total electrolyte mass of fluoroethylene carbonate (FEC) and 13% of the total electrolyte mass of lithium hexafluorophosphate (LiPF6) are added. Graphene is added as an additive, with the additive content accounting for 2% of the total electrolyte mass. The lithium-ion battery was subjected to cycle performance testing. At 20–30°C, it was charged at a constant current rate of 0.9–1.1C to 4.45–4.55V, then charged at a constant voltage rate of 0.045–0.055C to 4.45–4.55V, and then discharged at a discharge rate of 0.9–1.1C to 2.9–3.1V. After repeating this charge-discharge cycle 500 times, the capacity retention rate was not less than 70%, indicating good cycle performance.

[0030] This application also provides a method for preparing the above-mentioned ternary single-crystal cathode material, comprising: adding a complexing agent and a surfactant to a nickel-cobalt-manganese solution containing nickel compound, cobalt compound, and manganese compound to obtain a mixed solution; spray-drying the mixed solution to obtain a spray material; thermally decomposing the spray material in an oxygen-containing atmosphere to obtain an oxide precursor; and sintering the oxide precursor with a lithium source to obtain a ternary single-crystal cathode material.

[0031] According to the inventor's research and analysis: Nickel-cobalt-manganese salt in a mixed solution is sprayed into spheres under spray drying to obtain nickel-cobalt-manganese salt particles, i.e., spray material. In this process, the complexing agent helps improve the density (compactness) of the spray material, and the surfactant helps improve the particle integrity. The synergistic effect of both ensures that the spray material maintains high particle size distribution, preventing particle damage and ensuring high integrity and support. This results in a low particle size distribution width (SPAN), dense structure, stable and uniform spray material, i.e., nickel-cobalt-manganese salt particles. During the thermal decomposition (pre-sintering) of the aforementioned low-SPAN, dense, stable and uniform spray material, the complexing agent can refine the crystal lattice. To ensure the production of oxide precursors (oxide salts) with suitable crystallinity, surfactants can make the oxide precursor particles more uniform, ensuring the production of oxide precursors with low SPAN, suitable crystallinity, dense structure, uniformity without segregation, and low shrinkage (i.e., the volume ratio of oxide to sprayed material), namely nickel-cobalt-manganese oxide salts. The aforementioned oxide precursors with low SPAN, suitable crystallinity, dense structure, uniformity without segregation, and low shrinkage are mixed with a lithium source and then sintered (lithium-coated sintering). Without water washing, a ternary single-crystal cathode material (large single-crystal cathode material) with uniform particles, low SPAN value, large particle size, and low residual lithium content can be obtained. This ternary single-crystal cathode material exhibits good rate performance, and its d... O-Li-O The small size and dense structure of this ternary single-crystal cathode material give it high voltage resistance and structural stability, thus ensuring good cycle performance. Furthermore, due to the moderate crystallinity of the oxide precursor, lithium can more easily enter the precursor during lithium-ion sintering, reducing residual lithium content. This avoids the need for water washing to remove residual lithium from the ternary single-crystal cathode material, saving significant water resources, protecting the morphology of the material, simplifying the preparation process, reducing costs, avoiding complex equipment and conditions, minimizing environmental pollution, and ensuring the performance of the ternary single-crystal cathode material. This effectively solves the problems of complex preparation processes for large single crystals in existing technologies, requiring special equipment and conditions, and significantly increasing preparation costs.

[0032] Therefore, the preparation method of this application helps to obtain low SPAN value, large particle size, and d O-Li-O A small, dense, high-pressure-resistant, and low-residual-lithium ternary single-crystal cathode material is developed, exhibiting good cycle performance and rate performance.

[0033] The concentrations of nickel, cobalt, and manganese in the above nickel-cobalt-manganese solution can be 0.5–3 mol / L, for example, 0.5 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, or any combination thereof.

[0034] The molar ratio of nickel, cobalt and manganese in the above nickel-cobalt-manganese solution can be (6-8):1:(1-3), for example 6:1:1, 8:1:1, 6:1:3, 8:1:3 or any combination thereof.

[0035] In some embodiments, the above-mentioned nickel-cobalt-manganese solution is prepared by a method comprising at least the following steps: mixing a nickel compound, a cobalt compound, and a manganese compound in a molar ratio of nickel, cobalt, and manganese of (6-8):1:(1-3) and dissolving them in a solvent to obtain the nickel-cobalt-manganese solution. The solvent includes water.

[0036] As mentioned earlier, complexing agents help improve the density (compactness) of sprayed materials, while refining the crystal lattice to ensure the production of oxide precursors with moderate crystallinity, thereby ensuring the production of materials with low SPAN values, uniformity, low residual lithium content, and d O-Li-O A ternary single-crystal cathode material with low pressure resistance and high withstand strength has good cycle performance and rate performance.

[0037] In the mixed solution, the mass ratio of the complexing agent to the sum of the masses of nickel, cobalt, and manganese can be (5–20):100, for example, 5:100, 10:100, 15:100, 20:100, or any combination thereof. An appropriate amount of complexing agent helps improve reaction efficiency and product selectivity. This is because insufficient complexing agent may fail to effectively complex all target ions, leading to reduced reaction efficiency; while excessive amounts may cause side reactions or interfere with other necessary reaction steps. Therefore, controlling the mass of the complexing agent to meet the above range helps ensure reaction efficiency and high product selectivity, improves the density (compactness) of the sprayed material, and refines the crystal lattice to ensure a moderately crystalline oxide precursor, thereby ensuring a low SPAN value, uniformity, low residual lithium content, and d... O-Li-O A ternary single-crystal cathode material with low pressure resistance and high withstand strength has good cycle performance and rate performance.

[0038] In some embodiments, the complexing agent includes one or more of citric acid, tartaric acid, and sodium tripolyphosphate. Citric acid is preferred among the complexing agents. Citric acid contains three carboxyl groups (-COOH) and one hydroxyl group (-OH) in its molecule, allowing it to act as a polydentate ligand to form stable complexes with metal ions. For example, citric acid can ionize three protons to form three -COO- coordination functional groups. In addition, it has a hydroxyl group, thus acting as a tetradentate ligand. This allows it to form multiple five-membered chelate ring stereocoagulation structures with metal ions, further improving the density (compactness) of the spray-dried material. Simultaneously, it can refine the crystal lattice to ensure a moderately crystallizable oxide precursor, further improving the SPAN value, uniformity, residual lithium content, and d0 of the ternary single-crystal cathode material.O-Li-O This improves the cycling performance and rate performance of the ternary single-crystal cathode material by enhancing its properties such as withstand voltage and strength.

[0039] As mentioned earlier, surfactants help improve the particle integrity of sprayed materials and make the oxide precursor particles more uniform, thereby ensuring a low SPAN value, uniformity, and d O-Li-O A ternary single-crystal cathode material with low pressure resistance and high withstand strength has good cycle performance and rate performance.

[0040] In a mixed solution, the mass ratio of the surfactant to the sum of the masses of nickel, cobalt, and manganese can be (1–10):100, for example, 1:100, 2:100, 5:100, 7:100, 10:100, or any combination thereof. Surfactants can reduce the surface tension of liquids, making it easier for gases to form bubbles.

[0041] In some embodiments, the surfactant includes one or more of polyethylene glycol, potassium thiolate, and polyethylene glycol sulfate (PES). Polyethylene glycol is preferred among the surfactants mentioned above. Polyethylene glycol has a long ether chain, which gives it excellent solubility in water. Simultaneously, the oxygen atoms in the ether chain can form hydrogen bonds with water molecules, enhancing its hydrophilicity, resulting in good wetting and penetration properties. It can reduce the surface tension of water, making it easier for water to wet solid surfaces. Hydrophilic substances can improve the wetting properties of the sprayed material, thereby contributing to particle formation and integrity. During spray drying, hydrophilic substances typically bind to water molecules more quickly, which helps form uniform droplets during drying, resulting in particles with uniform size distribution and controllable morphology. This further contributes to improving the particle integrity of the sprayed material and makes the oxide precursor particles more uniform, further ensuring the production of particles with low SPAN values, uniformity, and d... O-Li-O This ternary single-crystal cathode material has low voltage and high withstand strength, and exhibits good cycle performance and rate capability.

[0042] During spray drying, the exhaust air temperature can be 150–220℃, such as 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, or any combination thereof, and the atomizer frequency can be 200–400Hz, such as 200Hz, 250Hz, 300Hz, 350Hz, 400Hz, which helps to obtain D 50Controllable, low SPAN, dense structure, controllable specific surface area (BET), stable structure, high particle retention rate and uniformity of aerosol particles. The above aerosol particles, after heat treatment, can yield oxide precursors with low SPAN, moderate crystallinity, dense structure, uniformity without segregation, and low shrinkage. This provides a basis for preparing oxide precursors with low SPAN, uniformity without segregation, and low shrinkage. O-Li-O The low-pressure, high-voltage ternary single-crystal cathode material provides the material basis.

[0043] In some embodiments, during spray drying, a Rongbo constant flow pump (model BT100-2J) is used to control the feed rate, keeping it between 20 and 35 Hz, for example, a range of 20 Hz, 25 Hz, 30 Hz, 35 Hz, or any combination thereof. Controlling the feed rate within this range helps to obtain D... 50 The reason for the controllable, low SPAN, dense structure, controllable specific surface area (BET), stable structure, and high and uniform particle retention of the sprayed material (sprayed powder particles) is that if the feed rate is too fast, the material to be dried may not be carried away by the hot air of the spray drying process in time, prolonging the residence time of the material (wet material) in the drying chamber. This may result in incomplete drying or uneven drying of the sprayed material, which is not conducive to maintaining the D of the sprayed material (sprayed powder particles). 50 It has excellent properties such as controllable, low SPAN, dense structure, controllable specific surface area (BET), stable structure, high and uniform particle retention. In addition, if the feeding speed is too slow, it will lead to low spray drying efficiency and reduce production efficiency.

[0044] In addition, during the spray drying process, the blower frequency can be 15-25Hz, and the induced draft fan frequency can be 10-50Hz, further ensuring the density of the sprayed material (sprayed material particles). 50 Controllable and possessing advantages such as low SPAN, dense structure, structural stability, and uniformity, this is because the blower's role is to provide hot air during the spray drying process. The blower frequency affects the temperature and flow rate of the hot air. Excessive blower frequency leads to excessively high hot air temperatures, which, while causing rapid drying of the material, may also cause thermal decomposition or deterioration of heat-sensitive materials, thus hindering the maintenance of D (density) of the sprayed material (sprayed material particles). 50 It boasts excellent properties such as controllable surface area, low SPAN, dense structure, controllable specific surface area (BET), stable structure, and high and uniform particle retention. However, excessively low blower frequency may lower the hot air temperature, insufficient to meet the requirements of spray drying, leading to decreased efficiency. The induced draft fan's role is to expel moisture from the spray-dried system; improper fan frequency settings can hinder moisture removal, increasing drying time and energy consumption. It may also cause excessive pressure within the drying chamber, affecting drying efficiency and equipment safety, all of which are detrimental to maintaining the D-value of the sprayed material (particles). 50It exhibits excellent properties such as controllable surface area, low SPAN, dense structure, controllable specific surface area (BET), stable structure, and high and uniform particle retention.

[0045] In some embodiments, the specific surface area (BET) of the above-mentioned aerosol (aerosol particles or nickel-cobalt-manganese salt) is 15–30 m². 2 / g. The inventors discovered in their research that by controlling the specific surface area of ​​the above-mentioned aerosol (aerosol particles or nickel-cobalt-manganese salt) within the above-mentioned range, it helps the aerosol (aerosol particles) maintain D... 50 The superior properties of the aerosol, such as controllable surface area (BET), low SPAN, dense structure, controllable specific surface area (BET), stable structure, and high and uniform particle retention, are attributed to the fact that the specific surface area (BET) of the aerosol affects its thermal decomposition and sintering performance in an oxygen-containing atmosphere. Specifically, if the BET of the aerosol is too small, its structure is too dense, leading to incomplete decomposition during subsequent sintering (e.g., incomplete decomposition of chlorine in chloride salts). Conversely, if the BET is too large, its structure is unstable, making it difficult to maintain a complete spherical structure during thermal decomposition and sintering, which is detrimental to maintaining the D-value of the aerosol particles. 50 It exhibits excellent properties such as controllable surface area, low SPAN, dense structure, controllable specific surface area (BET), stable structure, and high and uniform particle retention.

[0046] In some embodiments, the particle size distribution width (SPAN) of the above-mentioned spray material (spray material particles or nickel cobalt manganese salt) is less than or equal to 1.5, which lays a good material foundation for obtaining a ternary single crystal cathode material with uniform particles.

[0047] In the process of thermally decomposing the above-mentioned aerosol in an oxygen-containing atmosphere (e.g., air) to obtain the oxide precursor, the thermal decomposition temperature can be 500–800°C, for example, 500°C, 600°C, 700°C, 800°C, or any combination thereof. Within the above-mentioned thermal decomposition (pre-sintering) temperature range, the complexing agent can better refine the crystal lattice, reduce the crystallinity of the oxide precursor, and obtain an oxide precursor with moderate crystallinity. This moderately crystallinity oxide precursor is conducive to lithium intercalation during lithium supplementation sintering. At the same time, the surfactant can make the oxide precursor particles more uniform, ensuring a low SPAN, moderate crystallinity, dense and uniform structure, and low shrinkage (D of the aerosol). 50 and oxide precursor D 50 The difference between the D of the spray material and the D 50 The ratio of oxide precursors (to ensure a low SPAN value, uniformity, low residual lithium content, and d) is used to ensure the production of oxide precursors with low SPAN value, uniformity, and low residual lithium content. O-Li-O The low-pressure, high-voltage ternary single-crystal cathode material improves the cycle performance and rate performance of the ternary single-crystal cathode material.

[0048] In some embodiments, the thermal decomposition time can be 4–6 hours, for example, 4 hours, 5 hours, 6 hours, or any combination thereof. Understandably, the thermal decomposition time also affects the effectiveness of the thermal decomposition, thereby affecting the cycle performance and rate performance of the ternary single-crystal cathode material. Specifically, if the thermal decomposition time is too long, the thermal decomposition effect is excessive, leading to poor structural stability of the oxide precursor. Conversely, if the thermal decomposition time is too short, it is not conducive to the full utilization of the complexing agent and surfactant, thus failing to ensure the obtaining of an oxide precursor with low SPAN, moderate crystallinity, dense and uniform structure, and low shrinkage.

[0049] The molecular formula of the above oxide precursor can be NiCoMnO2, which has moderate crystallinity and low SPAN, making it suitable for preparing ternary single-crystal cathode materials with good rate performance (ternary large single-crystal materials).

[0050] In practice, the above-mentioned thermal decomposition system can be connected to an air extraction device so that the above-mentioned spray material undergoes thermal decomposition in an atmosphere containing oxygen (such as air).

[0051] In some embodiments, the above-mentioned oxide precursor satisfies: the D of the aerosol... 50 and oxide precursor D 50 The difference between the D of the spray material and the D 50 The ratio is less than or equal to 20%, meaning the shrinkage rate of the oxide precursor is less than or equal to 20%. The inventors discovered in their research that controlling the shrinkage rate of the oxide precursor to meet this range helps ensure the production of a product with low SPAN value, uniformity, low residual lithium content, and d... O-Li-O The reason for the low yield and high withstand voltage of ternary single-crystal cathode materials is that excessive shrinkage will lead to excessive crystallinity of the oxide precursor, which is not conducive to lithium ion intercalation during sintering (lithium ions have difficulty entering the layered structure). Conversely, excessively low yield indicates incomplete thermal decomposition, which is also not conducive to the effectiveness of complexing agents and surfactants. This, in turn, makes it difficult to obtain ternary single-crystal cathode materials with low SPAN value, uniformity, low residual lithium content, and low d... O-Li-O Ternary single-crystal cathode material with low pressure resistance and high withstand strength.

[0052] In some embodiments, the intensity of the nickel oxide peak in the X-ray diffraction (XRD) pattern of the oxide precursor is 2500–3500 counts, indicating that the oxide precursor has moderate crystallinity, which facilitates the entry of lithium during the subsequent lithium supplementation sintering process, helps to reduce the residual lithium content of the ternary single-crystal cathode material, and improves its rate performance. In addition, due to the moderate crystallinity of the oxide precursor, lithium can effectively enter the crystal lattice to form a good ternary layered structure. The support of the complexing agent will be inherited by the ternary single-crystal cathode material (ternary single-crystal material), ensuring that the ternary single-crystal cathode material particles have good voltage resistance and can improve the cycle performance of the ternary single-crystal cathode material.

[0053] In some embodiments, the intact particle retention rate of the above-mentioned oxide precursor reaches more than 85%. This intact particle retention rate is obtained by measuring the number of intact particles among 100 particles using high-magnification SEM.

[0054] In the process of sintering the oxide precursor with the lithium source to obtain the ternary single crystal cathode material, the sintering temperature can be 900 to 1000℃, such as 900℃, 950℃, 1000℃ or any combination thereof, and the sintering time can be 8 to 16h, such as 8h, 9h, 10h, 12h, 14h, 16h or any combination thereof.

[0055] The ratio of the sum of the amounts of nickel, cobalt, and manganese in the oxide precursor to the amount of lithium in the lithium source is 1:(1 to 1.1); that is, the molar ratio of nickel, cobalt, manganese, and lithium can be 1:(1 to 1.1), for example, 1:1, 1:1.02, 1:1.03, 1:1.04, 1:1.05, 1:1.1, or any combination thereof. In the preparation method system provided in the embodiments of this application, a ternary single-crystal cathode material with low residual lithium content and good rate performance and cycle performance can be obtained.

[0056] In some embodiments, the lithium source described above includes lithium hydroxide.

[0057] In some embodiments, the nickel compound includes nickel chloride, such as NiCl2 or NiCl2·6H2O; the cobalt compound includes cobalt chloride, such as CoCl2 or CoCl2·6H2O; and the manganese compound includes manganese chloride, such as MnCl2 or MnCl2·4H2O. Correspondingly, the nickel-cobalt-manganese solution includes nickel-cobalt-manganese chloride, and the spray material includes nickel-cobalt-manganese chloride particles (chloride salt). The above-mentioned nickel-cobalt-manganese solution can be prepared by a method including at least the following process: mixing nickel chloride, cobalt chloride, and manganese chloride in a molar ratio of nickel, cobalt, and manganese of (6-8):1:(1-3) and dissolving them in a solvent to obtain a nickel-cobalt-manganese chloride solution. The solvent may include water.

[0058] The technical challenge of oxidizing nickel cobalt manganese chloride to nickel cobalt manganese oxide through heat treatment (pre-sintering) lies in the significant differences in the decomposition temperatures of nickel chlorides (such as nickel chloride), cobalt chlorides (such as cobalt chloride), and manganese chlorides (such as manganese chloride). Manganese chloride decomposes at around 400℃, while nickel chloride decomposes at around 680℃. When these three are oxidized together through heat treatment, problems such as the inability of the three to coexist and the segregation of large manganese particles may occur. Furthermore, high-temperature dechlorination can lead to excessively high crystallinity of the oxide precursor (oxide), preventing lithium from entering and thus affecting the uniformity and electrochemical performance of the ternary single-crystal cathode material (single-crystal ternary material). To address the aforementioned issues, this application embodiment enhances the structural stability of the spray material (i.e., chloride salt) during the spray drying stage by adding complexing agents and surfactants (dispersants). Simultaneously, by coordinating specific spray drying parameters (e.g., induced draft temperature, atomizer frequency, feed rate, blower frequency, or induced draft fan frequency), the independence and integrity of the spray material particles (i.e., chloride salt particles) are increased, resulting in better support for the complete spray material particles (i.e., chloride salt particles). Then, during heat treatment (high-temperature oxidation), the highly supportive spray material particles (i.e., chloride salt particles) restrict manganese grain growth, reduce the crystallinity (peak intensity of the main peak) of the oxide precursor (oxide), and decrease the size of the oxide precursor particles. The independent, complete spray material particles further ensure the uniformity of the oxide precursor (oxide) particles. Because the oxide precursor has moderate crystallinity, lithium can effectively enter the lattice of the oxide precursor to form a good ternary layered structure. The supporting properties of the complexing agent will be inherited by the ternary single crystal cathode material (ternary single crystal material), ensuring that the ternary single crystal cathode material particles have good voltage resistance and improving the cycle performance of the ternary single crystal cathode material.

[0059] This application also provides a positive electrode sheet, which includes the above-described ternary single-crystal positive electrode material or the ternary single-crystal positive electrode material prepared according to the above-described preparation method.

[0060] The positive electrode sheet in this application specifically includes a positive current collector and a positive active layer formed of ternary single crystal positive electrode material disposed on the surface of the positive current collector.

[0061] In the specific preparation of the positive electrode sheet, for example, the ternary single-crystal positive electrode material of the present application embodiment can be dispersed with a conductive agent and a binder in an appropriate amount of N-methylpyrrolidone (NMP) solvent, and thoroughly stirred and mixed to form a uniform positive electrode slurry; the positive electrode slurry is uniformly coated on the positive electrode current collector, and after drying, rolling and slitting, the positive electrode sheet is obtained. In one specific embodiment, the positive electrode active layer comprises, by mass percentage, 70-99 wt% ternary single-crystal positive electrode material, 0.5-15 wt% conductive agent, and 0.5-15 wt% binder, and further comprises 80-98 wt% ternary single-crystal positive electrode material, 1-10 wt% conductive agent, and 1-10 wt% binder.

[0062] The positive current collector can be made of at least one of aluminum foil or nickel foil; the conductive agent can be selected from at least one of carbon black, acetylene black, graphene, Ketjen black, and carbon fiber; and the binder can be selected from at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polyethylene, polypropylene, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, ethylene oxide-containing polymers, polyvinylpyrrolidone, and polyurethane.

[0063] This application also provides a lithium-ion battery, which includes the above-mentioned positive electrode sheet.

[0064] As can be imagined, the lithium-ion battery in this application embodiment, in addition to the above-mentioned positive electrode, also includes a negative electrode, an electrolyte, and a separator.

[0065] The embodiments of this application do not strictly limit the negative electrode active material in the negative electrode sheet. It can be at least one of the negative electrode active materials commonly used in lithium-ion batteries, such as graphite, hard carbon, soft carbon, mesophase carbon microspheres, silicon-based negative electrode materials (mainly including silicon suboxide and silicon-carbon negative electrode), and tin-based negative electrode materials (mainly including tin and tin alloy).

[0066] The embodiments of this application do not strictly limit the selection of electrolyte, and may include one or more of the solvents commonly used in lithium-ion battery electrolytes, as well as the electrolyte lithium salts commonly used in lithium-ion electrolytes. For example, the solvent may be ethylene carbonate, propylene carbonate, butene carbonate, fluoroethylene carbonate (FEC), dimethyl carbonate (DMC), diethyl carbonate (DEC), difluoroethylene carbonate (DFEC), dipropyl carbonate, methyl ethyl carbonate (EMC), ethyl acetate, ethyl propionate, propyl acetate, propyl propionate, sulfolane, γ-butyrolactone, etc.; the lithium salt may be one or more of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0067] The embodiments of this application do not strictly limit the choice of separator material. It can be one of the separator materials commonly used in lithium-ion batteries, such as polypropylene separator (PP), polyethylene separator (PE), polypropylene / polyethylene double-layer composite membrane (PP / PE), polyimide electrospun separator (PI), polypropylene / polyethylene / polypropylene triple-layer composite membrane (PP / PE / PP), cellulose nonwoven separator, and separator with ceramic coating.

[0068] In the preparation of lithium-ion batteries, the positive electrode, separator, and negative electrode are wound or stacked to obtain a bare cell, which is then packaged into a pre-stamped aluminum-plastic film bag. After the packaged battery is dried at 85°C, the electrolyte is injected into the dried battery. After the battery is placed, formed, and resealed, the preparation of the lithium-ion battery is completed.

[0069] Cyclic performance tests were conducted on the above-mentioned lithium-ion batteries. The test results showed that the capacity retention rate could reach more than 88%, and the cycle performance was good. The specific test methods are described in the Examples section and will not be repeated here.

[0070] The present application will now be described in more detail through specific embodiments.

[0071] Example 1

[0072] This embodiment provides a method for preparing a ternary single-crystal cathode material, including:

[0073] 1) Mix NiCl2·6H2O, CoCl2·6H2O, and MnCl2·4H2O in a nickel, cobalt, and manganese molar ratio of 6:1:3 and dissolve them in water to obtain a nickel cobalt manganese chloride solution; the sum of the concentrations of nickel, cobalt, and manganese in this nickel cobalt manganese chloride solution is 1 mol / L;

[0074] 2) Add citric acid and polyethylene glycol to the above nickel-cobalt-manganese chloride solution to obtain a mixed solution; wherein the mass ratio of citric acid to the sum of the masses of nickel, cobalt, and manganese is 15:100, and the mass ratio of polyethylene glycol to the sum of the masses of nickel, cobalt, and manganese is 5:100.

[0075] 3) The above mixed solution is spray-dried to obtain spray material; wherein, during the spray drying process, the induced draft temperature is 180℃, the feed rate is 25Hz (the feed rate is controlled by a Rongbo constant flow pump (model BT100-2J), the atomizer frequency is 400Hz, the blower frequency is 20Hz, and the induced draft fan frequency is 20Hz.

[0076] 4) The above spray material was thermally decomposed in air at a temperature of 700°C for 6 hours to obtain an oxide precursor.

[0077] 5) The above oxide precursor and lithium hydroxide were mixed in a molar ratio of the sum of the amounts of nickel, cobalt and manganese in the oxide precursor to the amount of lithium in the lithium hydroxide of 1:1.05 and then sintered at a temperature of 970℃ for 12 hours to obtain a ternary single crystal cathode material.

[0078] Example 2

[0079] This embodiment is basically the same as Embodiment 1, except that:

[0080] In step 1), the molar ratio of nickel, cobalt, and manganese is adjusted to 8:1:1;

[0081] In step 2), the mass ratio of citric acid to the sum of the masses of nickel, cobalt, and manganese is adjusted to 20:100, and the mass ratio of polyethylene glycol to the sum of the masses of nickel, cobalt, and manganese is adjusted to 10:100.

[0082] In step 3), the exhaust temperature is adjusted to 175℃, the atomizer frequency is adjusted to 350Hz, and the exhaust fan frequency is adjusted to 15Hz.

[0083] In step 5), the molar ratio of the sum of the amounts of nickel, cobalt, and manganese in the oxide precursor to the amount of lithium in the lithium hydroxide is adjusted to 1:1.03, and the sintering temperature is adjusted to 800℃.

[0084] All other conditions remain unchanged.

[0085] Example 3

[0086] This embodiment is basically the same as Embodiment 1, except that:

[0087] In step 2), the mass ratio of citric acid to the total mass of nickel, cobalt, and manganese is adjusted to 5:100;

[0088] In step 3), the atomizer frequency is adjusted to 500Hz and the blower frequency is adjusted to 15Hz.

[0089] In step 5), the sintering temperature is adjusted to 960℃;

[0090] All other conditions remain unchanged.

[0091] Example 4

[0092] This embodiment is basically the same as Embodiment 1, except that:

[0093] In step 2), the mass ratio of citric acid to the sum of the masses of nickel, cobalt, and manganese is adjusted to 20:100, and the mass ratio of polyethylene glycol to the sum of the masses of nickel, cobalt, and manganese is adjusted to 15:100.

[0094] In step 3), the induced draft temperature is adjusted to 175℃, the feed rate is adjusted to 20Hz (using a Rongbo constant flow pump (model BT100-2J) to control the feed rate), the atomizer frequency is adjusted to 350Hz, the blower frequency is adjusted to 18Hz, and the induced draft fan frequency is adjusted to 16Hz.

[0095] In step 5), the sintering temperature is adjusted to 960℃;

[0096] All other conditions remain unchanged.

[0097] Example 5

[0098] This embodiment is basically the same as Embodiment 1, except that:

[0099] In step 2), the mass ratio of citric acid to the sum of the masses of nickel, cobalt, and manganese is adjusted to 5:100, and the mass ratio of polyethylene glycol to the sum of the masses of nickel, cobalt, and manganese is adjusted to 2:100.

[0100] In step 3), the induced draft temperature is adjusted to 200℃, the feed rate is adjusted to 30Hz (using a Rongbo constant flow pump (model BT100-2J) to control the feed rate), the atomizer frequency is adjusted to 400Hz, and the induced draft fan frequency is adjusted to 30Hz.

[0101] All other conditions remain unchanged.

[0102] Example 6

[0103] This embodiment is basically the same as Embodiment 1, except that in step 2), tartaric acid is used instead of citric acid; other conditions remain unchanged.

[0104] Example 7

[0105] This embodiment is basically the same as Embodiment 1, except that in step 2), sodium tripolyphosphate is used to replace citric acid; other conditions remain unchanged.

[0106] Example 8

[0107] This embodiment is basically the same as Embodiment 1, except that in step 2), potassium thiolate is used instead of polyethylene glycol; other conditions remain unchanged.

[0108] Example 9

[0109] This embodiment is basically the same as Embodiment 1, except that in step 2), polyethylene glycol sulfate is used instead of polyethylene glycol; other conditions remain unchanged.

[0110] Example 10

[0111] This embodiment is basically the same as embodiment 1, except that in step 3), the induced draft temperature is adjusted to 150°C; other conditions remain unchanged.

[0112] Example 11

[0113] This embodiment is basically the same as embodiment 1, except that in step 3), the induced draft temperature is adjusted to 220℃; other conditions remain unchanged.

[0114] Example 12

[0115] This embodiment is basically the same as embodiment 1, except that in step 3), the induced draft temperature is adjusted to 140℃; other conditions remain unchanged.

[0116] Example 13

[0117] This embodiment is basically the same as embodiment 1, except that in step 3), the induced draft temperature is adjusted to 230°C; other conditions remain unchanged.

[0118] Example 14

[0119] This embodiment is basically the same as embodiment 1, except that in step 3), the atomizer frequency is adjusted to 200Hz; other conditions remain unchanged.

[0120] Example 15

[0121] This embodiment is basically the same as embodiment 1, except that in step 3), the atomizer frequency is adjusted to 300Hz; other conditions remain unchanged.

[0122] Example 16

[0123] This embodiment is basically the same as embodiment 1, except that in step 3), the atomizer frequency is adjusted to 190Hz; other conditions remain unchanged.

[0124] Example 17

[0125] This embodiment is basically the same as embodiment 1, except that in step 3), the atomizer frequency is adjusted to 410Hz; other conditions remain unchanged.

[0126] Example 18

[0127] This embodiment is basically the same as embodiment 1, except that in step 4), the temperature of thermal decomposition is adjusted to 500℃; other conditions remain unchanged.

[0128] Example 19

[0129] This embodiment is basically the same as embodiment 1, except that in step 4), the temperature of thermal decomposition is adjusted to 800℃; other conditions remain unchanged.

[0130] Example 20

[0131] This embodiment is basically the same as embodiment 1, except that in step 4), the temperature of thermal decomposition is adjusted to 460°C; other conditions remain unchanged.

[0132] Example 21

[0133] This embodiment is basically the same as Embodiment 1, except that in step 4), the temperature of thermal decomposition is adjusted to 830°C; other conditions remain unchanged.

[0134] Comparative Example 1

[0135] This comparative example is basically the same as Example 1, except that:

[0136] Citric acid and polyethylene glycol are not used, while other conditions remain unchanged;

[0137] The specific process includes:

[0138] 1) Mix NiCl2·6H2O, CoCl2·6H2O, and MnCl2·4H2O in a nickel, cobalt, and manganese molar ratio of 6:1:3 and dissolve them in water to obtain a nickel cobalt manganese chloride solution; the sum of the concentrations of nickel, cobalt, and manganese in this nickel cobalt manganese chloride solution is 1 mol / L;

[0139] 2) The above mixed solution is spray-dried to obtain spray material; wherein, during the spray drying process, the exhaust air temperature is 180℃, the feed speed is 25Hz (the feed speed is controlled by a Rongbo constant flow pump (model BT100-2J), the atomizer frequency is 400Hz, the blower frequency is 20Hz, and the exhaust fan frequency is 20Hz.

[0140] 3) The above spray material was thermally decomposed in air at a temperature of 700°C for 6 hours to obtain an oxide precursor.

[0141] 4) The above oxide precursor and lithium hydroxide were mixed in a molar ratio of the sum of the amounts of nickel, cobalt and manganese in the oxide precursor to the amount of lithium in the lithium hydroxide of 1:1.05 and then sintered at a temperature of 970℃ for 12 hours to obtain a ternary single crystal cathode material.

[0142] Comparative Example 2

[0143] This comparative example is basically the same as Example 1, except that:

[0144] The aerosol material is not thermally decomposed; it is directly mixed with lithium hydroxide and then sintered. The specific process includes the following steps:

[0145] 1) Mix NiCl2·6H2O, CoCl2·6H2O, and MnCl2·4H2O in a nickel, cobalt, and manganese molar ratio of 6:1:3 and dissolve them in water to obtain a nickel cobalt manganese chloride solution; the sum of the concentrations of nickel, cobalt, and manganese in this nickel cobalt manganese chloride solution is 1 mol / L;

[0146] 2) Add citric acid and polyethylene glycol to the above nickel-cobalt-manganese chloride solution to obtain a mixed solution; wherein the mass ratio of citric acid to the sum of the masses of nickel, cobalt, and manganese is 15:100, and the mass ratio of polyethylene glycol to the sum of the masses of nickel, cobalt, and manganese is 5:100.

[0147] 3) The above mixed solution is spray-dried to obtain spray material; wherein, during the spray drying process, the induced draft temperature is 180℃, the feed rate is 25Hz (the feed rate is controlled by a Rongbo constant flow pump (model BT100-2J), the atomizer frequency is 400Hz, the blower frequency is 20Hz, and the induced draft fan frequency is 20Hz.

[0148] 4) The above-mentioned spray material and lithium hydroxide were mixed in a molar ratio of the sum of the amounts of nickel, cobalt and manganese in the oxide precursor to the amount of lithium in the lithium hydroxide at 1:1.05, and then sintered at a temperature of 970℃ for 12 hours to obtain a ternary single crystal cathode material.

[0149] Comparative Example 3

[0150] This comparative example is basically the same as Example 1, except that citric acid is not used in this comparative example; the specific differences are as follows.

[0151] Step 2) is adjusted to "add polyethylene glycol to the above nickel-cobalt-manganese chloride solution to obtain a mixed solution; wherein the mass ratio of polyethylene glycol to the total mass of nickel, cobalt and manganese is 5:100"; other conditions remain unchanged.

[0152] Comparative Example 4

[0153] This comparative example is basically the same as Example 1, except that polyethylene glycol is not used in this comparative example; the specific differences are as follows.

[0154] Step 2) is adjusted to "Add citric acid to the above nickel-cobalt-manganese chloride solution to obtain a mixed solution; wherein the mass ratio of citric acid to the total mass of nickel, cobalt and manganese is 15:100"; other conditions remain unchanged.

[0155] Experimental Example 1

[0156] 1. The following parameters of the above embodiments and comparative examples were tested:

[0157] 1) Specific surface area (BET) of the sprayed material: measured by TriStar II 3020 fully automatic three-station specific surface area and porosity analyzer; the specific results are shown in Table 1;

[0158] 2) Particle size distribution width (SPAN) of spray-dried materials, particle size distribution width (SPAN) of oxide precursors (pre-sintered materials), and particle size distribution width (SPAN) of ternary single-crystal cathode materials: according to SPAN = (D 90 -D 10 ) / D 50 The SPAN was calculated; the specific results are shown in Tables 1 and 2.

[0159] 3) Shrinkage rate of oxide precursor (pre-burned material): D of sprayed material 50 and oxide precursor D 50 The difference between the D of the spray material and the D 50 The ratio of D before and after heat treatment (pre-firing) characterizes the ratio of D before and after heat treatment (pre-firing). 50 The percentage change; see Table 1 for specific results;

[0160] 4) The intensity of the nickel oxide peak (crystallization or 43° NiO peak intensity) in the X-ray diffraction (XRD) pattern of the oxide precursor (pre-burned material): using nλ=2*d*sinθ, where λ is the incident wavelength, d is the interplanar spacing, and θ is the diffraction angle, the peak intensity of the nickel oxide is then found; the specific results are shown in Table 1.

[0161] 5) Integrity of oxide precursor (pre-burned material): 100 particles were randomly selected by SEM at high magnification, and the proportion of intact particles was calculated manually. Integrity particles are those that are observed to be unbroken, uncracked, and have a complete shape (e.g., round) with the naked eye. The specific results are shown in Table 1.

[0162] 6) Residual lithium content of ternary single-crystal cathode material: The following steps are performed to detect the residual lithium content: In a sealed conical flask, m1g of ternary cathode material and m2g of boiled distilled water are mixed to form a solution; the air inside the flask is purged using nitrogen; the solution is stirred magnetically at room temperature and allowed to stand; the mixed solution is quickly filtered into the flask using a needle filter to prepare the test solution; m3g of the test solution is taken out and mixed with another batch of boiled distilled water, and dynamic potentiometric titration is performed, using HCl as the titrant, and the volumes V1 and V2 corresponding to the jump points are recorded; the contents of Li2CO3 and LiOH are calculated using the following formulas: W1=C*(V2-V1)*73.89 / 1000=(m1*m3 / m2)*100%; W2=C*(2V1-V2)*23.941 / 1000 / (m1*m3 / m2)*100%;

[0163] W1: Mass fraction of Li2CO3, in g / L; W2: Mass fraction of LiOH, in g / L; C: Concentration of HCl, in mol / L; m1: Mass of ternary cathode material, in g; m2: Mass of distilled water, in g; m3: Mass of the test solution, in g; See Table 2 for specific results;

[0164] 7) D of ternary single-crystal cathode materials 50 The particle size was measured using a Malvern particle size analyzer, the Brownian motion velocity of the particles was obtained by analyzing the fluctuation of light intensity, and the particle size was obtained by the Stokes-Einstein equation; the specific results are shown in Table 2.

[0165] 8) Dielectric strength of ternary single-crystal cathode material: Measured using a particle strength tester, with D selected as the optimal value. 50 Ternary single-crystal cathode material particles larger than or equal to 3 μm were subjected to pressure recording. 50 Pressure data when particles of different sizes show obvious breakage were collected from multiple points, and the average value was calculated. The specific results are shown in Table 2.

[0166] 9) The distance d between Li atoms and O atoms in two adjacent layers of a ternary single-crystal cathode material O-Li- O The crystal structure of the ternary single-crystal cathode material (before charging) was tested and analyzed using X-ray diffraction and Bragg's law calculation: [2d sinα = n]. Here, (d) is the interplanar spacing, (α) is the diffraction angle, (n) is an integer (diffraction order), and (α) is the wavelength of the X-rays. When X-rays pass through the sample, they interact with the electron cloud within the sample. When X-rays are incident on the crystal planes, some X-rays are scattered by the crystal plane atoms, forming diffraction. X-rays conforming to Bragg's law are enhanced. As the sample is slowly rotated on a rotating stage, the diffraction angle changes, thus recording a series of data on the diffraction intensity changing with (α). These data, after processing and analysis, yield information related to the crystal structure, such as the cell parameter c, crystal plane orientation, and interplanar spacing d, where the interplanar spacing d is the lithium layer spacing d. O-Li-O The specific results are shown in Table 2;

[0167] 10) Chemical composition of ternary single-crystal cathode material: ICP analyzer was used to measure the proportions of Ni, Co, Mn, and Li; the specific results are shown in Table 2.

[0168] 11) Scanning electron microscope (SEM) images of ternary single-crystal cathode materials: Figure 1 shows the SEM image of the ternary single-crystal cathode material of Example 1, Figure 2 shows the SEM image of the ternary single-crystal cathode material of Comparative Example 1, and Figure 3 shows the SEM image of the ternary single-crystal cathode material of Comparative Example 2.

[0169] 2. Test Results

[0170] Table 1. Specific surface area and SPAN of the sprayed material; SPAN, shrinkage rate, 43°NiO peak intensity, and intact particle size of the oxide precursor (pre-burned material).

[0171] Analysis of the table above shows that: Comparative Example 1 does not use complexing agents and surfactants, Comparative Example 2 does not undergo thermal decomposition, and Comparative Example 3 does not use citric acid. The sprayed materials of Comparative Examples 1-3 have excessively large specific surface areas and large SPAN values. Among them, the pre-calcined materials of Comparative Examples 1 and 3 also have large SPAN values, high shrinkage rates, and low intact particle sizes. Comparing the data of the examples and comparative examples reveals that the preparation method of the present application examples helps to obtain materials with low SPAN values, large particle sizes, and low d... O-Li-O Small, dense, high-pressure-resistant, and low-residual-lithium-content ternary single-crystal cathode material.

[0172] Table 2. Residual lithium (lithium hydroxide / lithium carbonate), D of ternary single-crystal cathode materials 50 SPAN, compressive strength, d O-Li-O Chemical formula

[0173] Analysis of the table above shows that the residual lithium of the ternary single-crystal cathode material in the examples is significantly less than that in the comparative examples. Furthermore, the ternary single-crystal cathode material in the examples has a lower SPAN (spider surface area) and higher withstand voltage. O-Li- O =2.0A~3.5A. The ternary single-crystal cathode materials in Comparative Examples 1-3 have relatively low withstand voltage. The preparation method of this application helps to obtain low SPAN value, large particle size, and d O-Li-O Small, dense, high-pressure-resistant, and low-residual-lithium-content ternary single-crystal cathode material.

[0174] Experimental Example 2

[0175] After fabricating the ternary single-crystal cathode materials of the examples and comparative examples into cathode sheets, they were assembled with anode sheets, electrolyte, and separator according to the following method to obtain a coin cell. The method includes:

[0176] Each ternary single-crystal cathode material was mixed with conductive carbon black (SP) and PVDF in a weight ratio of 80%:10%:10%, and dispersed to obtain a cathode slurry. This cathode slurry was then coated onto an aluminum foil current collector and rolled to obtain an areal density of 1.5 g / cm³. 3 The positive electrode is then punched into a small disc with a diameter of 12mm using a film punch. After drying and weighing, the disc is assembled into a coin cell using a 2025 coin cell case, a Li metal disc as the negative electrode, and conventional high-voltage lithium cobalt oxide electrolyte in a glove box under an Ar protective atmosphere.

[0177] The cycle performance of the above-mentioned button cells was tested:

[0178] At 25℃, the capacitor was charged at a constant current rate of 0.1C to 4.3V, then charged at a constant voltage rate of 0.1C to 4.45V, and then discharged at a discharge rate of 0.1C to 2.5V. The discharge capacity Q1 (initial discharge capacity) during the first cycle was measured, and the results are shown in Table 3.

[0179] The rate performance of the above-mentioned button cells was tested:

[0180] The battery was charged and discharged at 25°C using a battery charge and discharge tester. The charge and discharge regime was as follows: constant current charging at 0.1C to 4.45V, then constant voltage charging at 4.45V until the current decreased to 0.02C, followed by resting for 5 minutes, and then constant current discharging at 0.2C to 2.5V. The discharge capacity Q was recorded. 0.2c After resting for 5 minutes, charge with a constant current of 0.2C to 4.45V, then switch to a constant voltage of 4.45V to charge until the current decreases to 0.02C. After resting for 5 minutes, discharge with a constant current of 3C to 2.5V, and record the discharge capacity Q. 3c The capacity retention rate can be calculated using the following formula: 3C discharge rate capacity retention rate = Q 3c / Q 0.2c ×100%, the results are shown in Table 3;

[0181] Experimental Example 3

[0182] After fabricating the positive electrode active materials from all embodiments and comparative examples into positive electrode sheets, they were assembled with negative electrode sheets, electrolytes, and separators according to the following method to obtain a lithium-ion battery. The method includes:

[0183] 1) The ternary single-crystal cathode material from the examples and comparative examples was mixed with conductive carbon black and PVDF at a weight ratio of 96%:2%:2%, and dispersed to obtain a cathode slurry. This cathode slurry was then coated onto an aluminum foil current collector, with a cathode areal density of 4.12 g / cm³. 3 The positive electrode sheet is prepared by rolling.

[0184] 2) Artificial graphite, styrene-diene rubber (SBR), sodium carboxymethyl cellulose, and conductive carbon black are mixed in a weight ratio of 94%:3%:2%:1%. The mixture is dispersed in water and then mixed using a double planetary mixer to obtain a negative electrode slurry. This slurry is coated onto a copper current collector, followed by rolling and drying to obtain the negative electrode sheet.

[0185] 3) Assemble the positive electrode, negative electrode, and separator into a lithium-ion battery and inject a non-aqueous electrolyte. The electrolyte is prepared by mixing ethylene carbonate (EC): diethyl carbonate (DEC): propylene carbonate (PC) in a mass ratio of 2:5:3. Then, add 5% fluoroethylene carbonate (FEC) and 13% lithium hexafluorophosphate (LiPF6) by mass, along with graphene as an additive, with the additive content accounting for 2% of the total electrolyte content.

[0186] The cycle performance of the above-mentioned lithium-ion batteries was tested:

[0187] At 25°C, the capacitor was charged at a constant current rate of 1C to 4.50V, then charged at a constant voltage rate of 0.05C to 4.50V, and finally discharged at a discharge rate of 1C to 3.0V. This charge-discharge cycle was repeated 500 times. The discharge capacity Q1 at the first cycle and the discharge capacity Q at the 500th cycle were measured. 500 The capacity retention rate Q after 500 cycles is calculated using the following formula: Capacity retention rate Q = Q 500 / Q1*100%, the results are shown in Table 3;

[0188] Table 3 Cycle performance and rate performance of button cells and lithium-ion batteries

[0189] Analysis of the data in the table above shows that the initial discharge capacity, rate performance, and cycle performance of the coin cell and lithium-ion battery in the embodiments are better than those of the comparative examples. The ternary single-crystal cathode material obtained by the preparation method of the embodiments of this application has better cycle performance and rate performance.

[0190] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A ternary single-crystal cathode material, characterized in that, D of the ternary single-crystal cathode material is greater than or equal to 3 pm 50 greater than or equal to 3 pm; The d O-Li-O = 2.0A~3.5A, wherein the d O-Li-O is the distance between the Li atom and the O atoms of the adjacent two layers; The withstand voltage of the ternary single-crystal cathode material is greater than or equal to 150 MPa.

2. The ternary single-crystal cathode material according to claim 1, characterized in that, The ternary single-crystal cathode material includes lithium, oxygen, and transition metal elements; the transition metal elements include nickel, cobalt, and manganese. The ternary single-crystal cathode material has a chemical formula of Li y Ni a Co b Mn c O2, wherein 0.98≤y≤1.10, 0.6≤a≤0.9, 0≤b≤0.4, and 0≤c≤0.4 And / or, the concentration of lithium hydroxide and the concentration of lithium carbonate in the ternary single-crystal cathode material are less than or equal to 800 ppm and 800 ppm, respectively. And / or, the particle size distribution width of the ternary single-crystal cathode material is 1.10 to 1.

30.

3. The ternary single-crystal cathode material of claim 1, wherein, The ternary single-crystal cathode material is charged at 20–30°C with a constant current of 0.9–1.1C to 4.45–4.55V, then charged at a constant voltage of 0.045–0.055C to 4.45–4.55V, and then discharged at a discharge rate of 0.9–1.1C to 2.9–3.1V. After repeating this charge-discharge cycle 500 times, the capacity retention rate is not less than 86%.

4. A method for producing the ternary single-crystal cathode material according to any one of claims 1 to 3, characterized in that include: A complexing agent and a surfactant are added to a nickel-cobalt-manganese solution containing nickel compounds, cobalt compounds, and manganese compounds to obtain a mixed solution; The mixed solution is spray-dried to obtain a spray powder; The aerosol was thermally decomposed in an oxygen-containing atmosphere to obtain an oxide precursor. The oxide precursor is mixed with a lithium source and then sintered to obtain the ternary single-crystal cathode material.

5. The preparation method according to claim 4, characterized in that, The complexing agent includes one or more of citric acid, tartaric acid, and sodium tripolyphosphate; And / or, the surfactant includes one or more of polyethylene glycol, potassium thiolate, and polyethylene glycol sulfate.

6. The preparation method according to claim 4, characterized in that, During the spray drying process, the exhaust air temperature is 150-220℃ and the atomizer frequency is 200-400Hz. and / or the specific surface area of the sprayable material is 15 to 30 m 2 / g; And / or, the particle size distribution width of the spray material is less than or equal to 1.

5.

7. The preparation method according to claim 4, characterized in that, The thermal decomposition temperature is 500–800°C, and the thermal decomposition time is 4–6 hours. And / or, the D of the aerosol 50 and the D of the oxide precursor 50 The difference between the D of the spray material and the D of the spray material 50 The ratio is less than or equal to 20%.

8. The preparation method according to claim 4, characterized in that, The intensity of the nickel oxide peak in the X-ray diffraction (XRD) pattern of the oxide precursor is 2500–3500 Counts.

9. A positive electrode sheet characterized by comprising: The positive electrode sheet includes the ternary single crystal positive electrode material according to any one of claims 1-3 or the ternary single crystal positive electrode material obtained by the preparation method according to any one of claims 4-8.

10. A lithium-ion battery, characterized by, The lithium-ion battery includes the positive electrode sheet as described in claim 9.

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